Infinitely variable power branching transmission with two operating modes

ABSTRACT

The invention concerns an infinitely variable power branching transmission with two operating modes, whereof the components are distributed between two power paths connecting in parallel the heat engine ( 1 ) to the vehicle wheels ( 3 ), said means including at least two planetary trains ( 5, 6 ) two electrical machines ( 2, 4 ), a reduction stage ( 7 ), and control means orienting differently the power between the transmission input and output based on the operating mode thereof. The invention is characterised in that it comprises two reduction stages ( 7 ) arranged in parallel between the two trains ( 5, 6 ) on the same power path, said two stages being respectively urged in the first and in the second operating transmission mode.

[0001] The present invention relates to a power-splitting transmissionwherein, regardless of how fast the internal combustion engine isspinning, a continuous variation from reverse gear to forward gear canbe achieved by passing through a special position known as “engagedneutral”, in which the speed of movement of the vehicle is zero.

[0002] More precisely, its object is a power-splitting infinitelyvariable transmission having two modes of operation, wherein theconstituent elements are distributed between two power trains thatprovide parallel connections between the internal combustion engine andthe wheels of the vehicle, these means including at least two epicyclicgear sets, two electrical machines, one reducing stage and control meansthat guide the power between the input and output of the transmissiondifferently depending on the mode of operation thereof.

[0003] Power-splitting transmissions may be based on three knownprinciples or modes of power splitting. According to the first mode,known as “coupled input”, the transmission is provided with a pair ofpower-splitting pinions that splits the power at the input of themechanism and with an epicyclic “assembler” gear set that recombines thepowers at the output of the mechanism. The control element is avariator.

[0004] In transmissions with power splitting of the “coupled output”type, there is provided, for example, a power-dividing planetary gearset at the input of the mechanism and a power-reassembling pair ofpinions at the output of the mechanism, the control element again beinga variator.

[0005] Finally, in transmissions with power splitting of the “twomatching points” type, a first power-dividing epicyclic gear set can bepositioned at the gearbox input, while a second power-reassemblingepicyclic gear set is disposed at the gearbox output, the controlelement again being a variator.

[0006] The traditional infinitely variable transmissions (IVT) use onlyone or two of these three operating principles.

[0007] From U.S. Pat. Nos. 5,558,589 and 5,935,035 there are knowninfinitely variable transmissions with two modes of operation combiningat least two planetary gear sets, two mode-changing clutches and oneelectrical variator, and using as the first mode of operation theprinciple of power splitting with coupled output.

[0008] According to these publications, the mode-changing means arepositioned outside the epicyclic gear sets.

[0009] The significance in having two modes of operation available liesin the increase of the range of transmission ratios and in thepossibility of reducing the size of the electrical machines.

[0010] Nevertheless, in these known two-mode architectures, the modechanges are achieved by multiple-disk clutches disposed on thetransmission output, and for this reason are accompanied by torque joltsthat are sensed as unpleasant by the users.

[0011] Another disadvantage of the architectures described in thesepublications lies in their complexity, which is related in particular tothe presence of at least two clutches and one brake.

[0012] The object of the present invention is to provide apower-splitting infinitely variable transmission with two modes ofoperation, wherein the architecture is simpler than that of the usualtransmissions of the same type, electrical machines of small dimensionsare used, and the changes of mode are not accompanied by any torquejolt.

[0013] To achieve this object, it is proposed that the mode changes beaccomplished by acting on the internal mechanical linkages of thetransmission situated between the two gear sets.

[0014] According to the invention, at least two reducing stages aredisposed between the two epicyclic gear sets for this purpose, thesestages being engaged in the first and second modes of operationrespectively. These two reducing stages are disposed in parallel betweenthe two gear sets on the same power train.

[0015] According to other characteristics of the invention, the twoelectrical machines are mounted in series on the same power train, andthe two reducing stages are mounted in parallel between the twoelectrical machines.

[0016] Without departing from the scope of the invention, the electricalmachines may also be connected to an energy-storage unit or to agenerator.

[0017] According to the preferred embodiments of the invention, theproposed transmission may contain seven, six or five reducing stages, ofwhich two are disposed outside the epicyclic gear sets.

[0018] Other characteristics and advantages of the present inventionwill become clearly evident upon reading the description hereinafterwith reference to the attached drawings, in which FIGS. 1 to 10illustrate ten special embodiments thereof.

[0019] The transmission of FIG. 1 is composed of two epicyclic gear sets5, 6, seven reducing stages 7, two mode-changing systems 8 and 9, whichmay be either claw couplings or multiple-disk clutches, and twoelectrical machines 2, 4, which together constitute a variator.

[0020] This transmission has four input and output connections, whichcan be connected respectively to internal combustion engine 1, to wheels3 and to two electrical machines 2 and 4.

[0021] Internal combustion engine 1 is connected to one reducing stage7. Wheels 3 are connected to two reducing stages 7. A first electricalmachine 2 of the variator is connected to one reducing stage 7, and asecond electrical machine 4 is connected to one reducing stage 7 and totwo mode-changing systems 8 and 9.

[0022] Three reducing stages are connected to the first epicyclic gearset 5. Four reducing stages are connected to the second epicyclic gearset 6. One reducing stage is connected to each mode-changing system 8and 9.

[0023] The transmission illustrated by FIG. 1 therefore contains sevenreducing stages, of which five are disposed between and two are disposedoutside the two epicyclic gear sets.

[0024] Internal combustion engine 1 is connected to epicyclic gear set 5via one reducing stage, and wheels 3 are connected to each epicyclicgear set 5, 6 via one reducing stage.

[0025] This transmission has two modes of operation with two matchingpoints. In the first mode, first mode-changing system 8, connected totwo reducing stages on the one hand and to one electrical machine 4 onthe other hand, is open. This first branch is therefore disengaged,while the second branch, which contains second mode-changing system 9and, just as the first branch, is connected to two reducing stages andto electrical machine 4, is closed.

[0026] Conversely, in the second mode of operation, the first branch isclosed and the second branch is open.

[0027]FIG. 2 shows the same elements as on FIG. 1. Just as theforegoing, this transmission has four input and output connections,which can be connected respectively to internal combustion engine 1, towheels 3, to first electrical machine 2 and to second electrical machine4. In this case the internal combustion engine is connected to eachepicyclic gear set 5, 6 by one reducing stage 7, and wheels 3 areconnected to a single epicyclic gear set 5 by one reducing stage.

[0028] Just as that in FIG. 1, the transmission of FIG. 2 is providedwith two modes of operation having two matching points, depending onwhether first and second mode-changing systems 8, 9, which are disposedin analogous manner, are open or closed.

[0029] The transmissions illustrated by FIGS. 3 to 6 contain sixreducing stages, of which four are disposed between and two are disposedoutside the two epicyclic gear sets.

[0030] In FIG. 3, internal combustion engine 1 is connected via onereducing stage 7 to an epicyclic gear set 5.

[0031] In FIG. 4, internal combustion engine 1 is connected via a singlereducing stage 7 to two epicyclic gear sets 5, 6.

[0032] In FIG. 5, wheels 3 are connected to each epicyclic gear set. 5,6 via one reducing stage 7.

[0033] In FIG. 6, internal combustion engine 1 is connected to eachepicyclic gear set 5, 6 by one reducing stage 7.

[0034] The transmissions according to the invention and illustrated byFIGS. 7 and 8 contain five reducing stages, of which three are disposedbetween and two are disposed outside the two epicyclic gear sets 5, 6.

[0035] In FIG. 7, internal combustion engine 1 is connected to oneepicyclic gear set 5 via one reducing stage 7.

[0036] In FIG. 8, internal combustion engine 1 is connected to twoepicyclic gear sets 5, 6 by a single reducing stage 7.

[0037] Finally, the transmissions of FIGS. 9 and 10, in common withthose of FIGS. 1 and 2, contain seven reducing stages 7, of which fiveare disposed between and two are disposed outside the two epicyclic gearsets 5, 6.

[0038] In FIG. 9, wheels 3 are connected to epicyclic gear set 6 by tworeducing stages 7 in series, while in FIG. 10 it is engine 1 that isconnected to gear set 6 by two reducing stages 7 in series.

[0039] In conclusion, each of the non-limitative embodiments of theinvention described hereinabove contains the two epicyclic gear sets,the two electrical machines and a certain number of reducing stages. Thecorresponding transmissions also contain control means (notillustrated), which guide the power between the input and the output ofthe transmission differently depending on the mode of operation thereof.The two electrical machines are mounted in series on the same powertrain, and can be connected to a generator or to an energy-storage unit(not illustrated).

[0040] In all cases, the arrangement of two parallel branches betweenthe two electrical machines, each containing one reducing stage and amode-changing system, ensures that two modes of operation are availableat two operating points, depending on the branch being used.

1. A power-splitting infinitely variable transmission having two modesof operation, wherein the constituent elements are distributed betweentwo power trains that provide parallel connections between the internalcombustion engine (1) and the wheels (3) of the vehicle, these meansincluding at least two epicyclic gear sets (5, 6), two electricalmachines (2, 4), one reducing stage (7) and control means that guide thepower between the input and output of the transmission differentlydepending on the mode of operation thereof, characterized in that it isprovided with two reducing stages (7) disposed in parallel between thetwo gear sets (5, 6) on the same power train, these two stages beingengaged respectively in the first and second modes of operation of thetransmission.
 2. A transmission according to claim 1, characterized inthat the two electrical machines (2, 4) are mounted in series on thesame power train.
 3. A transmission according to claim 1 or 2,characterized in that the two reducing stages (7) are mounted inparallel between the two electrical machines (2, 4).
 4. A transmissionaccording to claim 1, 2 or 3, characterized in that the electricalmachines (2, 4) are connected to an energy-storage unit.
 5. Atransmission according to claim 1, 2 or 3, characterized in that the twoelectrical machines (2, 4) are connected to an electrical energygenerator.
 6. A transmission according to one of the preceding claims,characterized in that it contains seven reducing stages (7), of whichfive are disposed between and two are disposed outside the two epicyclicgear sets (5, 6).
 7. A transmission according to claim 6, characterizedin that the internal combustion engine (1) is connected to the epicyclicgear set (5) via one reducing stage (7), and in that the wheels (3) areconnected to each epicyclic gear set (5, 6) via one reducing stage (7).8. A transmission according to claim 6, characterized in that theinternal combustion engine (1) is connected to each epicyclic gear set(5, 6) by one reducing stage (7), and in that the wheels (3) areconnected to a single epicyclic gear set (6) by one reducing stage (7).9. A transmission according to claim 6, characterized in that the wheels(3) are connected to an epicyclic gear set (6) by two reducing stages(7) in series.
 10. A transmission according to claim 6, characterized inthat the engine (1) is connected to an epicyclic gear set (6) by tworeducing stages (7) in series.
 11. A transmission according to one ofclaims 1 to 5, characterized in that it contains six reducing stages(7), of which four are disposed between and two are disposed outside thetwo epicyclic gear sets (5, 6).
 12. A transmission according to claim11, characterized in that the internal combustion engine (1) isconnected via one reducing stage (7) to an epicyclic gear set (5).
 13. Atransmission according to claim 11, characterized in that the internalcombustion engine (1) is connected via a single reducing stage (7) toboth epicyclic gear sets (5, 6).
 14. A transmission according to claim11, characterized in that the wheels (3) are connected to each epicyclicgear set (5, 6) via one reducing stage (7).
 15. A transmission accordingto claim 11, characterized in that the internal combustion engine (1) isconnected to each epicyclic gear set (5, 6) by one reducing stage (7).16. A transmission according to one of claims 1 to 5, characterized inthat it contains five reducing stages (7), of which three are disposedbetween and two are disposed outside the two epicyclic gear sets (5, 6).17. A transmission according to claim 16, characterized in that theinternal combustion engine (1) is connected to an epicyclic gear set (5)via one reducing stage (7).
 18. A transmission according to claim 16,characterized in that the internal combustion engine (1) is connected toboth epicyclic gear sets (5, 6) by a single reducing stage (7).